The stator of a dynamoelectric machine such as an electric motor or generator typically includes a core of magnetic material having an axially extending bore for receiving a rotor. The core typically is formed from a plurality of identical laminations which are aligned and arranged in a stack held together by clips. Each lamination includes a plurality of teeth which extend radially into the bore. Slots between each of the teeth extend radially outwardly from the bore. The ends of the teeth and the open ends of the slots define the periphery of the bore.
A plurality of coils formed from insulated conductive wire are inserted into selected core slots with portions of the coils at the ends of the core forming end turn regions. The coils are interconnected to form coil groups or poles. The conductive wires which form the coils, sometimes referred to as stator windings, typically are coated with a varnish or an enamel so that a tough protective coating is formed around each wire. The coating is required so that each wire is well insulated from the other wires. Improvements to or reduction of damage to such coating facilitates improved motor performance by, for example, reducing field failures. Damage often occurs during insertion of the coils into the core slots because of misplacement.
To insert the coils into the stator core slots, it is known to form coil groups with coil forms, then transfer the coil groups to coil insertion (or injection) tooling, and then move the coil groups from the coil insertion tooling to a stator with portions thereof located in stator slots. Coil injection apparatus for inserting the coils into the stator slots is described, for example, in U.S. Pat. Nos. 3,949,464 and 6,282,775. Known tooling for such apparatus typically include a base having a plurality of radially arranged and spaced blades extending from an upper surface of the base. The blades are arranged in a circular array.
Partnering with the coil injection process, most of the electric motor industry uses the xe2x80x9cshedxe2x80x9d type coil winders. The principle of the xe2x80x9cshedxe2x80x9d winder is that it wraps wire around a tapered coilform step and then pushes this wire down the taper into the tooling as the next turn of wire is wrapped above it. Stand-alone xe2x80x9cshedxe2x80x9d winders will wind coils into a xe2x80x9ctransfer toolxe2x80x9d. The process of winding today uses the transfer tool to transfer the wound coils from a winding machine to the inserting machine. The operator uses the transfer tool to manually transfer the coils to the tooling for use with the injection/insertion machine.
With the advent of improved machine tool controls, the xe2x80x9cshedxe2x80x9d type winder has become more versatile providing the motor manufacturers with additional savings on smaller production runs. A standalone xe2x80x9cshedxe2x80x9d winder can be changed from one lamination to another within two (2) minutes. Stack height changes and pole configuration changes can be made automatically. This flexibility is crucial since the winding process sets the pace for the entire stator assembly line. However, misplacement of coils when transferring coil groups from transfer tooling to the insertion tooling is the single largest manufacturing defect in any stator winding operation. Misplacement of coils within insertion tooling results in incorrect rotation and operation of the motors and significant speed and torque changes.
One method to improve product quality while reducing direct labor in stator assembly is to integrate the winding and injecting operations into a common machine. Instead of winding into a transfer tool (for manual transfer of the coils to the injector tooling), these machines wind the stator coils directly into the correct slots of injection tooling. The insulated stator core is manually placed within the machine and its alignment is verified.
Customers using these machines experience very high machine utilization and tooling life. This is due to the fact that operator error is practically eliminated since the machine automatically winds the stator coils into the correct slots and the stator alignmerit is automatically verified prior to it being placed on the injection tooling. When this technology is coupled with automated set-up features, the result is a highly productive, flexible and reliable cell at the heart of the stator assembly process. This is the goal of motor manufacturers regardless of their labor costs. However, these integrated machines are expensive and in the event of a machine malfunction, or need for production of different winding designs, a winding/injecting/ automation machine limits manufacturing flexibility.
Accordingly, it would be desirable and advantageous to provide a method and apparatus for eliminating misplacement of coils for insertion in a stator during manufacturing, thus reducing the scrap attributed to defective stators. It would also be desirable and advantageous to provide a method and apparatus which is low in cost, both for manufacture and maintenance, and which eliminates a need for a human operator to transfer wound coils from the winding operation to the insertion operation during the manufacturing process.
The above discussed and other drawbacks and deficiencies are overcome or alleviated by a method and apparatus for winding and placing windings on the magnetic core of a motor without transferring the windings prior to insertion. The method comprising: loading a wire stripper assembly having a first wire stripper including a substantially circular circumferentially extending continuous shoulder and a second wire stripper, into a bore of coil winding/injection device in a random angular orientation relative to such device; winding turns of wire into gaps established by the device directly from a corresponding winding machine such that a clearance between the first wire stripper continuous shoulder and the bore is approximately one-half the diameter of a smallest diameter wire included in the windings; positioning a slotted magnetic core on the device with slots of the core aligned with gaps of the device; moving the stripper assembly and engaging selected portions of the wire turns with the continuous shoulder within the bore of the device and axially moving said wire turns along said device and into slots of the core by engaging the wire stripper assembly with only portions of the wire turns positioned within the bore of the device.
In an alternative embodiment, a single device for winding and injecting coils for a motor without manual transfer of the coils comprises a plurality of gap defining elongate blades arranged in a circular array, the blades configured to have the coil groups wound thereon from a winding machine such that portions of each of the coils are located in gaps between adjacent ones of the blades and segments of each of the coils extend across the interior of said circular array of blades; and a stripper assembly movable axially within the circular array of blades, the stripper assembly includes a first stripper having a disk having an outer diameter less than an inner diameter of the circular array, a first surface of the first stripper configured to contact at least one segment of at least one coil which extends across an interior of the circular array of blades and to move at least the one coil axially along the blades without contacting the portions of the one coil in the gaps between the blades.